The role of kWh- based billing in fast charging infrastructures
Integrating energy metering and legal metrology into EV fast charging stations is essential to deliver accuracy, transparency and trust
The transition from internal combustion engines (ICEs) to electric vehicles (EVs) sets a range of new challenges for societies, particularly in determining how and where to deliver the most efficient EV charging. Because EVs can be charged in numerous locations and through various methods , it is essential for end users to have a thorough understanding of these charging options . Drivers also need to be provided with straightforward services if they are to embrace the concept of widespread decarbonis ation of the transport sector.
The charging method used depends on a balance of several factors: the user’s available time at a charging spot, the amount of energy required for vehicle use and the cost and availability of charging equipment. The power of the vehicle’s onboard charger is limited for reasons of weight and cost, making it suitable for recharging at home or at the workplace using alternating current (AC). However, to achieve the higher charging speeds that widespread adoption of EVs requires, fast chargers are able to charge the vehicle’s battery using direct current (DC). These fast chargers effectively cut down charging times and are deployed in public charging hubs or along highways.
The expansion of the EV fast charging infrastructure raises new questions. For instance, how can drivers be assured they’re billed fairly, adhering to the principle of ‘pay for what you get,’ when charging their EVs? How can major charge point operators verify that their infrastructure adheres to regulations governing the sale of electricity to end users, especially in DC? Similarly, what measures must entities like supermarkets, city hubs or e-truck depots take to ensure their future charging systems can invoice end users or third-party companies in a precise and controlled manner?
Energy metering
The short answer is through energy metering. Metering of energy used during a charging session provides fairness and transparency for end users and third parties, fostering trust and confidence for new technology acceptance. It ensures individuals are billed based on the actual energy consumed during the charging process (measured in kilowatts per hour or kWh). Regulations of the commercial exchange of electricity and metrology standards offer safeguards not only for the EV owner but also for the owner of a charging infrastructure because they can rely on and monitor performance levels.
The aim of metrology legislation is to make sure all concerned parties can have confidence in the measurements taken. Metrologically controlled instruments are part of our everyday life; we use them to drink water, eat fruits, consume electricity in our household, trade hydrogen, run traditionally fuelled vehicles… and much more. Metrologically verified results are fundamental to all transactions involving weight and measurement and the process of exchanging electricity between DC fast chargers and EVs uses the same principle. It is applicable not just to the public charging infrastructure but also to non-public areas where several entities use billing based on real energy consumption.
Consequently, guidelines and standards are put in place across regions to ensure consistency in the roll-out of DC fast charging infrastructures. In Europe, the ’Fit for 55’ legislative package includes the Alternative Fuel Infrastructure Directive (AFIR), which establishes rules to ease usage and provide standardised services throughout the EU, including the adoption of kWh-based payment of charging sessions for EVs. Similarly, in the US, the National Electric Vehicle Infrastructure (NEVI) Formula Program incorporates rules to fund the deployment of DC fast charging infrastructure s, adhering to the same requirements of kWh-based payment.
In addition, because charging station operators have an interest in minimising energy losses during the charging process, kWh billing encourages the development of more energy-efficient charging technologies. This, in turn, yields overall benefits for the EV community. In practice, the total price calculation of a fast-charging session will use kWh as a base – in compliance with metrology regulations – but may also apply time-based pricing in case EVs remain parked to the charging post after being fully charged (to discourage vehicles from occupying charging points unnecessarily).
The idea behind the integration of DC energy metering in fast chargers is that accurate measurement of electricity must be taken at the interface between the charger and the EV in DC. This means that the kWh value measurement accurately represents the energy consumed by the vehicle during the charging process. Consequently, the end user is not billed for any conversion losses or losses incurred through wiring that are beyond their control. Energy measurement is performed by robust and accurate hardware under all conditions and data is protected against any modification and transmitted to the e-mobility service providers, who are ultimately responsible for the final price calculation and billing process.
To ensure measurement performance and metering protection mechanisms are properly implemented, standards and directives oversee the design and production of metering equipment. This includes the MID directive 2014/32/EU, which sets out the fundamental requirements for active energy metering at the European level, as well as specific national requirements in countries like Germany (Eichrecht) and France (Décision n° 22.00.570.001.1). However, the concept of DC metering is still novel for a considerable number of laboratories and regulatory bodies.
Seamlessly incorporated
When the EV sector was in its infancy, charging fees were based on time, with drivers paying for the length of their charging sessions. This resulted in unfair billing, depending on the charging speed offered by the EV and the chargers. But today the trend is to adopt kWh-based pricing that is based on the actual energy consumed. Armed with accurate, real-time data, EV owners have a greater understanding of their charging sessions which means they can make more cost-based decisions.
To achieve true kWh-based pricing, listed and certified energy metering systems need to be seamlessly incorporated into EV chargers. Drawing on its expertise and heritage in electrical measurement, LEM is a major player in the EV charging landscape, delivering tailored DC energy metering solutions for this specific application. LEM has played a leading role in advancing DC energy metering by working intensively and closely with regulatory authorities and manufacturers of EV fast chargers. The company has been pioneering in obtaining and advocating certifications like MID 2014/32/EU for DC, achieving certification for calibration laws in the French and German markets. Furthermore, LEM’s solutions provide a swift response to meet the needs of the North American market, delivering high-performance solutions that comply with CTEP certification requirements for all EV DC fast chargers.
As a leader in this sector when it was just developing, LEM was able to ascertain and identify all emerging customer needs and gather valuable market data which enabled it to become the first company to develop a DC billing meter for fast charging stations. So forward-thinking was LEM that it forged strong relationships with several of the main regulating bodies to discuss regulations that were not even in place at the time. Because Europe was leading the way in terms of regulations, LEM started with a European standard and individual country standards one by one, recognising that each market had its own specific rules and requirements.
The company’s range of direct current billing meters (DCBMs) makes it possible for electric vehicle charging station (EVCS) operators to offer end users the desired kWh-based charging experience. Designed to simplify the process of integration into complex and modular EV rapid chargers, the meters feature a display that shows real-time measurements, energy and legal data. Intended for retrofitting as well as new DC fast charging stations delivering up to 600A and 1000V DC, the DCBMs ensure secure communications, authentic billing, easy connectivity to backend systems and a faster certification process in compliance with metrology regulations.
As well as Eichrecht and the 2014/32/EU MID directive, French regulation n° 22.00.570.001.1, the DCBMs comply with EN 50470-1:2006, EN 50470-3:2006, PTB-A 50.7, PTB-A 20.1, CISPR32 Class-B emission, IEC 62052-11:2003, IEC 61000-6-2:2016, IEC 61000-6-3:2016, UL 61010-1, CAN/CSA-C22.2 No. 61010-1 and UL94-V0. This means the DCBMs are certified for use across Europe and North America.
Equitable, fair and transparent
DC billing meters are essential in order to provide billing for DC-based EV rapid charging that is equitable, fair and transparent. They are the only way to ensure EV users and third parties receive precise, legally controlled and reliable energy measurements for billing purposes. They also ensure the global EV fast charging infrastructure is future-proof when it comes to changing requirements. As a result, LEM’s customers can effortlessly implement kWh -based charging, allowing them to concentrate on the demanding process of infrastructure deployment and expansion.
The first DC energy meters on the market with a split module concept (patent pending) which allows for compact and flexible design options, LEM’s DCBMs consist of a sensor unit which measures bidirectional energy flows, voltage, current and busbar temperature, sending this data securely to the meter unit. The meter unit receives and processes the measurement data, manages charging sessions and formats and authenticates the data so that the measurement is trustworthy to proceed to billing.
An increasing number of organisations aiming to establish kWh-based charging solutions for end users and fleets now recognise the importance of using a certified energy metering system when setting up an electric vehicle charging infrastructure. Initially offering two versions of the DCBM – 400A or 600A – LEM has already seen the units installed extensively across Europe, where they are playing a crucial role in enabling kWh-based charging. Continually pioneering in the market, LEM has recently developed the DCBM 100 80A bi-directional (V2G) meter for DC destination charging applications in the 30kW range (with obtained certification for MID and Eichrecht). As an example of the company always adapting its product offering to provide solutions to customers’ needs and satisfying metrology regulations as they evolve, this compact meter ensures easy connectivity to Cloud services as well as a faster certification process in compliance with all relevant standards.
In summary, kWh-based billing ensures fairness. This is vital for the successful implementation of a reliable DC fast charging infrastructure of EVs, ensuring consistent services across different countries and widespread transparency. End users and third parties will be able to trust that their charging sessions are billed with integrity and security and that the data they interact with is consistently accurate and up-to-date. Only by employing the most robust and certified solutions can operators expand the charging infrastructure at a rate that that can keep up with rapidly growing demand.
Florent Balboni is the Global Product Manager for energy metering solutions and EV charging markets at LEM
